Optical receiver and station-side device

Abstract

An optical receiver includes a transimpedance amplifier that converts a current signal output from a light-receiving element that receives an optical signal into a voltage signal, and has a variable conversion gain when performing the conversion, a gain control circuit that detects the bottom voltage of the voltage signal output from the transimpedance amplifier and controls the conversion gain of the transimpedance amplifier based on a result of the detection, and a signal detection circuit that outputs a signal detection signal indicating a signal detection result of whether or not an optical signal is being received. When the signal detection signal indicates a transition from an optical signal non-reception state to an optical signal reception state, the gain control circuit terminates the control of the conversion gain and holds the value of the conversion gain at a point in time when the control of the conversion gain is terminated.

What is claimed is: 
     
         1 . An optical receiver comprising:
 a transimpedance amplifier to convert a current signal output from a light-receiving element to receive an optical signal into a voltage signal, the transimpedance amplifier having a variable conversion gain when performing the conversion;   a gain control circuit to detect a bottom voltage of the voltage signal output from the transimpedance amplifier and control the conversion gain of the transimpedance amplifier based on a result of the detection; and   a signal detection circuit to output a signal detection signal indicating a signal detection result of whether or not an optical signal is being received, wherein,   the gain control circuit includes an operational amplifier used to detect the bottom voltage,   when the signal detection signal indicates a transition from a non-reception state that is a state in which an optical signal is not being received to a reception state that is a state in which an optical signal is being received, the gain control circuit terminates the control of the conversion gain and holds a value of the conversion gain at a point in time when the control of the conversion gain is terminated, and   the operational amplifier operates based on the voltage signal input when the signal detection signal indicates the non-reception state, and holds an output voltage constant when the signal detection signal indicates the reception state.   
     
     
         2 . An optical receiver comprising:
 a transimpedance amplifier to convert a current signal output from a light-receiving element co receive an optical signal into a voltage signal, the transimpedance amplifier having a variable conversion gain when performing the conversion;   a gain control circuit to detect a bottom voltage of the voltage signal output from the transimpedance amplifier and control the conversion gain of the transimpedance amplifier based on a result of the detection;   a signal detection circuit to output a signal detection signal indicating a signal detection result of whether or not an optical signal is being received; and   a convergence determination circuit co determine whether the control of the conversion gain by the gain control circuit is in a convergent state or a non-convergent state, wherein,   the gain control circuit includes an operational amplifier used to detect the bottom voltage,   when the signal detection signal indicates a transition from a non-reception state that is a state in which an optical signal is not being received to a reception state that is a state in which an optical signal is being received, or when the convergence determination circuit determines that the control of the conversion gain is in the convergent state, the gain control circuit terminates the control of the conversion gain and holds a value of the conversion gain at a point in time when the control of the conversion gain is terminated, and   the operational amplifier operates based on the voltage signal input when the signal detection signal indicates the non-reception state, and holds an output voltage constant when the signal detection signal indicates the reception state.   
     
     
         3 . The optical receiver according to  claim 1 , wherein
 upon input of a reset signal indicating that input of a packet signal is completed, the operational amplifier changes from a state of holding the value of the conversion gain to a state of changing the conversion gain according to intensity of an optical reception signal.   
     
     
         4 . The optical receiver according to  claim 2 , wherein
 upon input of a reset signal indicating that input of a packet signal is completed, the operational amplifier changes from a state of holding the value of the conversion gain to a state of changing the conversion gain according to intensity of an optical reception signal.   
     
     
         5 . The optical receiver according to  claim 1 , comprising:
 a delay circuit to delay the signal detection signal output from the signal detection circuit.   
     
     
         6 . The optical receiver according to  claim 2 , comprising:
 a delay circuit to delay the signal detection signal output from the signal detection circuit.   
     
     
         7 . The optical receiver according to  claim 3 , comprising:
 a delay circuit to delay the signal detection signal output from the signal detection circuit.   
     
     
         8 . The optical receiver according to  claim 4 , comprising:
 a delay circuit to delay the signal detection signal output from the signal detection circuit.   
     
     
         9 . A station-side device comprising the optical receiver according to  claim 1 . 
     
     
         10 . A station-side device comprising the optical receiver according to  claim 2 . 
     
     
         11 . A station-side device comprising the optical receiver according to  claim 3 . 
     
     
         12 . A station-side device comprising the optical receiver according to  claim 4 . 
     
     
         13 . A station-side device comprising the optical receiver according to  claim 5 . 
     
     
         14 . A station-side device comprising the optical receiver according to  claim 6 . 
     
     
         15 . A station-side device comprising the optical receiver according to claim.  7 . 
     
     
         16 . A station-side device comprising the optical receiver according to  claim 6 .